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Preface.                                   ix

welcomed which attempts to lay the demon of l rule of
thumb,' the autocrat of even my own apprentice days. To
encourage exactitude and prevent one source of error in
the application of formulae, I commence with a ' synopsis
of lettering,' and have here introduced what I believe to be
much needed, the retention of a certain letter wherever
possible solely for one purpose. Though this was not
always entirely practicable, I yet venture to think that
some improvement has been effected. It is unfortunate,
for example, that /stands both for stress and acceleration ;
but at           it need not be adopted both for tons and

pounds. I have, therefore, employed it for tons only*
Again, velocity per minute and per second are better
separately distinguished, as in the text, by the letters
V and v respectively.

While never introducing mathematics unnecessarily, I
have stated all the 'steps' that space permitted in such
mathematics as have been introduced, and the latter will
be found of but an elementary character, involving only
simple equations, fractions, and the use of tables of
and logarithms. The substitution of graphic treatment for
the higher mathematics in many cases will, I thinkr be
appreciated by most students.

As regards the order of Part II., the Strength of
Materials without doubt comes first, to be followed by
Energy and Kinematics; these all assist in the treatment
of Prime Movers worked by           or liquid*. With the

knowledge acquired frdm Fart L and his own                                 i

in the workshop, supplemented by the theory of Part IL,                |

the student should be able to commence the study of                

original design, for he is now in, acquaintance          with                 1

what theory directs and the woricihop                                             \

Regarding itiuMmtlonft* 1 commenced with iht                             .     *

of admitting no' highly-shaded                               which*

showing nothing of Interior parti,' are only                  to

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